/*
 * Created on 9 Aug 2006
 * Created by Paul Gardner
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

package org.gudy.azureus2.core3.util;

public class FrequencyLimitedDispatcher {
    private AERunnable target;
    private long min_millis;

    private long last_run;
    private DelayedEvent delay_event;

    public FrequencyLimitedDispatcher(AERunnable _target, int _min_frequency_millis) {
        target = _target;
        min_millis = _min_frequency_millis;
    }

    public void setSingleThreaded() {
        final AERunnable old_target = target;

        target = new AERunnable() {
            private boolean running;
            private boolean pending;

            public void runSupport() {
                synchronized (this) {

                    if (running) {

                        pending = true;

                        return;
                    }

                    running = true;
                }

                try {
                    old_target.runSupport();

                } finally {

                    boolean was_pending;

                    synchronized (this) {

                        running = false;

                        was_pending = pending;

                        pending = false;
                    }

                    if (was_pending) {

                        dispatch();
                    }
                }
            }
        };
    }

    public void dispatch() {
        long now = SystemTime.getMonotonousTime();

        boolean run_it = false;

        synchronized (this) {

            if (delay_event == null) {

                long delay = min_millis - (now - last_run);

                if (now < last_run || delay <= 0) {

                    last_run = now;

                    run_it = true;

                } else {

                    // run too recently

                    delay_event = new DelayedEvent("FreqLimDisp", delay, new AERunnable() {
                        public void runSupport() {
                            long now = SystemTime.getMonotonousTime();

                            synchronized (FrequencyLimitedDispatcher.this) {

                                last_run = now;

                                delay_event = null;
                            }

                            target.run();
                        }
                    });
                }
            }
        }

        if (run_it) {

            target.run();
        }
    }
}
